Acidic catalyst

ABSTRACT

Catalysts are disclosed having metal oxide support structures and acidic reaction sites. The reaction sites may be according to the general formula MxOyAlBrzX]−H+ where x is one or two; y is one or two; z is one or two; X is selected from Br or Cl; M is Al or Si and one or more of M, O and Al has a molecular bond with the metal oxide support structure.

This application claims the benefit of provisional application No.62/488,466 filed on Apr. 21, 2017 and entitled Acidic Catalyst.

This invention was made with government support under grant award numberCBET-1644895 awarded by the National Science Foundation. The governmenthas certain rights in the invention.

Acidic catalyst described herein may be used in hydrocarbon reactions.Certain acidic catalyst disclosed herein demonstrate super acidity andmay be capable of isomerizing alkanes at room temperature. Certainacidic catalyst disclosed herein may be useful in the oligomerization ofmethane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an acidification reaction.

FIG. 2 shows a reactor setup.

FIG. 3 shows chromatogram results for attempted oligomerizationreactions.

DETAILED DESCRIPTION Example Set 1A Initial Catalyst

Wet impregnation techniques may be used with various solvents to prepareacid catalysts. For example, supports may be impregnated by thedissolved aluminum halide precursors represented by the aluminum speciesof Table 1 in solvents of Table 1 at room temperature with refluxproducing the initial catalyst species shown in Table 1. The resultingcatalysts may then be filtered and dried under vacuum yielding solidacid catalysts represented by initial catalyst species Ai-Pi.

TABLE 1 Initial Support Solvent Al Species Augmented Acid Catalyst A_(i)Alumina Toluene AlCl₃ A_(a) B_(i) Alumina CCl₄ AlCl₃ B_(a) C_(i) AluminaToluene AlBr₃ C_(a) D_(i) Alumina CHBr₃ AlBr₃ D_(a) E_(i) Silica GelToluene AlCl₃ E_(a) F_(i) Silica Gel CCl₄ AlCl₃ F_(a) G_(i) Silica GelToluene AlBr₃ G_(a) H_(i) Silica Gel CHBr₃ AlBr₃ H_(a) I_(i) MCM-41Toluene AlCl₃ I_(a) J_(i) MCM-41 CCl₄ AlCl₃ J_(a) K_(i) MCM-41 TolueneAlBr₃ K_(a) L_(i) MCM-41 CHBr₃ AlBr₃ L_(a) M_(i) SBA-15 Toluene AlCl₃M_(a) N_(i) SBA-15 CCl₄ AlCl₃ N_(a) O_(i) SBA-15 Toluene AlBr₃ O_(a)P_(i) SBA-15 CHBr₃ AlBr₃ P_(a)

Example Set 1B Initial Catalyst

Vapor phase grafting techniques may also be used to prepare acidcatalysts. For example, supports and aluminum halide, separated byquartz wool, may be heated up to 300° C. inside an air free vessel orunder an inert atmosphere, allowing aluminum halide vapor to react withthe surface species of support producing the initial catalyst speciesshown in Table 1. The resulting catalysts may then be separated fromaluminum halide under vacuum yielding solid acid catalysts representedby initial catalyst species A_(i)-P_(i). In one example, not shown inTable 1, AlBr₃ was grafted onto ZSM-5 according to the method describedabove to produce an AlBr₃ modified ZSM-5 initial catalyst.

The supports used are not limited to the supports described in Table 1.Other supports consistent with the present disclosure may includezeolites and other similar supports. Such supports may be microporoussupports or mesoporous supports. Supports may be silica-based or theymay be alumina based. Inorganic supports may be used particularly whenelevated temperatures are contemplated for later uses of resultingcatalyst.

Example Set 2 Acidification

Initial catalyst species A_(i)-P_(i) may then be treated with HBr toform acid sites analogous to [H⁺/AlBr₄ ⁻] and [H⁺/AlCl₃Br⁻]. Examples ofHBr treatment that may be used to further acidify initial catalystspecies A_(i)-P_(i) include contacting initial catalyst speciesA_(i)-P_(i) with a flow of between 1% and 10% HBr gas in an inert gassuch as helium or argon for a duration between one and three hours atroom temperature. HBr concentrations may more broadly range between 0.1%and 20% HBr. Each of the HBr treatments occur at room temperature butmay be performed at higher temperatures potentially enhancing theacidity of the catalyst. For example, the HBr treatment may occurbetween 50° C. and 200° C. The product of the HBr treatment of initialcatalyst species A_(i)-P_(i) is the augmented acid catalyst A_(a)-P_(a).As an example, the silica gel based initial catalyst species G_(i) mayreact with HBr to yield G_(a) as follows:

G_(i)+HBr→G_(a)

That acidification of the initial catalyst to yield the augmented acidcatalyst may be generally characterized by the reaction depicted in FIG.1 with that figure showing the reaction sites of augmented acid catalystG_(a). Other augmented acid catalyst would vary from augmented acidcatalyst G_(a) based on the choice of support and aluminum species.Augmented acid catalyst G_(a), K_(a), O_(a) and C_(a) have been producedand verified in the laboratory according to the described methods andaugmented acid catalyst A_(a), B_(a), D_(a), E_(a), F_(a), H_(a), I_(a),J_(a), L_(a) M_(a), N_(a) and P_(a) along with other similar alumina andsilica based catalysts are prophetic embodiments that may be producedaccording the methods described herein.

The reactor set up of FIG. 2 may be used for the acidification reactionsof the present example set and in methane oligomerization. FIG. 2depicts Methane supply 10, Methane supply valve 13, HBr supply 16, HBrsupply valve 18, Helium supply 20, Helium supply valve 23, Tubularreactor 30, Catalyst bed 33, Condenser 40, Gas-liquid separation unit50, Liquid drain 53, Caustic wash vessel 60, Gas chromatograph valve 66,Gas chromatograph 68, Vent valve 70 and Vent 73. HBr acidification mayoccur by passing HBr and helium over Catalyst bed 33 in Tubular reactor30 such that the acidification of example set two is achieved. Causticwash vessel 60, which may contain a KOH solution, removes unreacted HBrfrom the effluent gas. Methane oligomerization may also be conducted inthe reactor setup as described herein.

Example Set 3 Forms

Augmented acid catalysts may take the form of catalysts having reactionsites according to one or more of the following general formulas:

In general formulas 1-4, X may be Br or Cl and M may be either Si or Al.Further, M would be molecularly bound to a support structure such asthose described herein. General formula 5 is a generalization of variousforms of the described reaction sites.

M_(x)O_(y)AlBr_(z)X]⁻H⁺  (5)

In general formula 5, x is selected from 1 and 2; y is selected from 1and 2; z is selected from 1 and 2; X is selected from Br and Cl; and Mis selected from Al and Si. Further, in general formula 5, one or moreof M, O and Al would have a molecular bond with the metal oxide supportstructure.

Example Set 4 Isomerization

Certain augmented acid catalyst may be characterized as superacids basedon the ability of those catalyst to isomerize n-butane into isobutane.As that term is used herein “superacid” designates compounds andcatalysts capable of n-butane isomerization at room temperature. Suchtesting may be conducted in a continuous flow reactor in which n-butaneflows over a bed of the subject catalyst at room temperature. In suchtesting, the augmented acid catalyst G_(a), K_(a) and O_(a) demonstratedsuper acidity and C_(a) did not demonstrate super acidity.

Example Set 5A Oligomerization Tests

Augmented acid catalyst A_(a)-P_(a) along with other similar catalystsmay be subjected to methane oligomerization methods or test such aspresented in FIG. 2. FIG. 2 depicts the general reaction setup of thepresent example set. The conversion of methane may be evaluated with agas chromatograph and other standard equipment for the evaluation ofhydrocarbon products. Higher molecular weight hydrocarbons may becaptured from Gas-liquid separation unit 50 and Caustic wash vessel 60for analysis. The contacting of the methane with the catalyst may occurat a variety of temperatures and pressures including room temperatureand atmospheric pressure. Further elevated temperatures, elevatedpressures or both may be used. For example, elevated temperatures andpressures commonly associated with conventional hydrocarbon processingmay be used. Each of initial catalyst species A_(i)-P_(i) and each ofaugmented acid catalyst A_(a)-P_(a) have significant potential utilityas acid catalysts or as superacid catalyst regardless of those compoundsability to oligomerize methane.

Augmented acid catalyst C_(a), G_(a), K_(a) and O_(a), each preparedusing the wet impregnation technique, have been tested for methaneoligomerization and did not demonstrate measured methane oligomerizationin preliminary tests. Augmented acid catalyst A_(a), B_(a), D_(a),E_(a), F_(a), H_(a), I_(a), J_(a), L_(a) M_(a), N_(a) and P_(a) are eachindividually significant candidates for successful methaneoligomerization and the prophetic methods of contacting the methane withthe augmented acid catalyst A_(a), B_(a), D_(a), E_(a), F_(a), H_(a),I_(a), J_(a), L_(a), M_(a), N_(a) and P_(a) are directly intended asmethods of the present disclosure. Oligomerization may have been maskedby trace organic compounds in reaction tests using catalyst preparedwith wet impregnation techniques and for that reason, augmented acidcatalyst C_(a), G_(a), K_(a) and O_(a) may still be candidates foroligomerization. Methane oligomerization, as described herein may begenerally characterized as the conversion of methane to higher molecularweight hydrocarbons and may proceed according to the followinggeneralized reaction in which n is greater than or equal to 2:

nCH₄→C_(n)H_(m) +xH₂

Example 5B Oligomerization

Methane gas was co-fed with HBr into Tubular reactor 30, as described inFIG. 1, such that the combined gas flowed over the AlBr₃ modified ZSM-5initial catalyst described in Example Set 1B. An analysis of the productgas indicated that oligomerization had occurred resulting in multiplehigher molecular weight hydrocarbon species. Further analysis ofproducts ruled out the HBr acting as a reactant.

Example Set 5C Oligomerization

In four separate attempted oligomerization reactions, using the reactionsetup of FIG. 1, methane gas was fed without HBr into a reactor suchthat the methane gas flowed over four catalysts. CH₄ was oligomerizedover the AlBr₃ supported on H-ZSM5, noted as “ABZ-5” and “Cat-1;” AlBr₃supported on SiO₂, noted as “ABSi” and “Cat-2;” unmodified H-ZSM5 notedas “Cat-3” and over sulfated zirconia, noted as “Cat-4.” Of the fourseparate attempted oligomerization reactions of the present example set,only AlBr₃ supported on H-ZSM5 produced a range of hydrocarbons, fromC₂-C₈, including ethylene, propylene, butenes, butane, pentenes, as wellas aromatics including benzene, toluene and xylenes. The other catalystsshowed no measurable products. Each of these four attemptedoligomerization reactions were conducted at approximately 300° C., 1atm, 9 L/gcat-hr. FIG. 3 shows a chromatograph that compares the fourCH₄ attempted oligomerization runs.

Accordingly, oligomerization may occur using an initial catalyst with orwithout the co-feeding of HBr and oligomerization may occur using anaugmented catalyst with or without the co-feeding of HBr.

As that phrase is used herein, a “mesoporous catalyst” is a catalysthaving an average pore diameter between 2 and 50 nm. As that phrase isused herein, a “microporous catalyst” is a catalyst having an averagepore diameter that is at most 2 nm. As that phrase is used herein, an“aluminum oxide based catalyst” is a metal oxide catalyst in whichaluminum is the elemental metal having the greatest individual weightpercent among all elemental metals present in the metal oxide catalyst.Alumina, for example would be an aluminum oxide based catalyst. As thatphrase is used herein, a “silicon oxide based catalyst” is a metal oxidecatalyst in which silicon is the elemental metal having the greatestindividual weight percent among all elemental metals present in themetal oxide catalyst. Silica Gel, MCM-41 and SBA-15 would each beconsidered silicon oxide based catalyst as that phrase is used herein.The phrases aluminum oxide based catalyst and silicon oxide basedcatalyst as used herein are intended to encompass augmented acidcatalyst A_(a)-P_(a). Silica-alumina mixed oxide catalysts may becharacterized as either aluminum oxide based catalyst or silicon oxidebased catalyst as those phrases are used herein based on the weight ofelemental metals present in the silica-alumina mixed oxide catalyst. Forexample, a zeolite according to the formula Na₂Al₂Si₃O₁₀.2H₂O would be asilicon oxide based catalyst. As used herein Si is treated as a metalfor the purposes of describing metal oxide catalyst, silicon oxide basedcatalyst, aluminum oxide based catalyst and the like.

Compositions of matter described herein may, for example, comprise acatalyst comprising a metal oxide support structure and an acidicreaction site such that the acidic reaction site has a compositionaccording to a general formula,

M_(x)O_(y)AlBr_(z)X]⁻H⁺;

in which x is 1 or 2; y is 1 or 2; z is 1 or 2; X is Br or Cl; M is Alor Si; one or more of M, O and Al has a molecular bond with the metaloxide support structure and the catalyst is an aluminum oxide basedcatalyst or a silicon oxide based catalyst. In a related example, thecatalyst may be a mesoporous catalyst. In a related example, thecatalyst may be a microporous catalyst. In a related example, thecatalyst may be an aluminum oxide based catalyst. In a further relatedexample, the catalyst may be a silicon oxide based catalyst. In afurther related example, X may be Br. In a further related example, Xmay be Cl. In a further related example, M may be Al. In a still furtherrelated example, M may be Si. In a still further related example, M maybe Si and X may be Br. In a still further related example, M may be Siand X may be Cl.

Compositions of matter described herein may, for example, comprise acatalyst comprising a metal oxide support structure and an acidicreaction site such that the acidic reaction site has a compositionaccording to a general formula,

in which X is Br or Cl; M is Al or Si; one or more of M and O has amolecular bond with the metal oxide support structure and the catalystis an aluminum oxide based catalyst or a silicon oxide based catalyst.In a related example, the catalyst may be a mesoporous catalyst. In arelated example, the catalyst may be a microporous catalyst. In arelated example, the catalyst may be an aluminum oxide based catalyst.In a further related example, the catalyst may be a silicon oxide basedcatalyst. In a further related example, X may be Br. In a furtherrelated example, X may be Cl. In a further related example, M may be Al.In a still further related example, M may be Si. In a still furtherrelated example, M may be Si and X may be Br. In a still further relatedexample, M may be Si and X may be Cl.

Compositions of matter described herein may, for example, comprise acatalyst comprising a metal oxide support structure and an acidicreaction site such that the acidic reaction site has a compositionaccording to a general formula,

in which X is Br or Cl; M is Al or Si; one or more of M and O has amolecular bond with the metal oxide support structure and the catalystis an aluminum oxide based catalyst or a silicon oxide based catalyst.In a related example, the catalyst may be a mesoporous catalyst. In arelated example, the catalyst may be a microporous catalyst. In arelated example, the catalyst may be an aluminum oxide based catalyst.In a further related example, the catalyst may be a silicon oxide basedcatalyst. In a further related example, X may be Br. In a furtherrelated example, X may be Cl. In a further related example, M may be Al.In a still further related example, M may be Si. In a still furtherrelated example, M may be Si and X may be Br. In a still further relatedexample, M may be Si and X may be Cl.

As that phrase is used herein, a “light hydrocarbon composition,” is acomposition comprising a one to four carbon atom hydrocarbon. Thus,natural gas would be an example of a light hydrocarbon composition.

Methods of reacting hydrocarbons described herein may comprise providinga light hydrocarbon composition having a first constituent molecule anda second constituent molecule; providing a catalyst; bringing thecatalyst in contact with the light hydrocarbon composition andconducting a chemical reaction in which the first constituent moleculereacts with the second constituent molecule to produce a productmolecule having a higher molecular weight than the first constituentmolecule; such that the catalyst is selected from an aluminum oxidebased catalyst and a silicon oxide based catalyst and such that thecatalyst is an acidic catalyst. In a related example, the catalyst maybe a mesoporous catalyst. In a related example, the catalyst may be amicroporous catalyst. In a related example, the catalyst may be analuminum oxide based catalyst. In a related example, the catalyst may bea silicon oxide based catalyst. In a related example, the conducting ofthe chemical reaction may be done in the presence of HBr. In a relatedexample, the first constituent molecule is methane and the secondconstituent molecule is methane.

The above-described embodiments have a number of independently usefulindividual features that have particular utility when used incombination with one another including combinations of features fromembodiments described separately. There are, of course, other alternateembodiments which are obvious from the foregoing descriptions, which areintended to be included within the scope of the present application.

What is claimed is:
 1. A composition of matter comprising: a. a catalystcomprising a metal oxide support structure and an acidic reaction site;b. wherein the acidic reaction site has a composition according to ageneral formula,M_(x)O_(y)AlBr_(z)X]⁻H⁺; c. wherein x is selected from 1 and 2; d.wherein y is selected from 1 and 2; e. wherein z is selected from 1 and2; f. wherein X is selected from Br and Cl; g. wherein M is selectedfrom Al and Si; h. wherein one or more of M, O and Al has a molecularbond with the metal oxide support structure and i. wherein the catalystis selected from an aluminum oxide based catalyst and a silicon oxidebased catalyst.
 2. The composition of matter of claim 1 wherein thecatalyst is a mesoporous catalyst.
 3. The composition of matter of claim1 wherein the catalyst is a microporous catalyst.
 4. The composition ofmatter of claim 1 wherein the catalyst is an aluminum oxide basedcatalyst.
 5. The composition of matter of claim 1 wherein the catalystis a silicon oxide based catalyst.
 6. The composition of matter of claim1 wherein X is Br.
 7. The composition of matter of claim 1 wherein X isCl.
 8. The composition of matter of claim 1 wherein M is Al.
 9. Thecomposition of matter of claim 1 wherein M is Si.
 10. The composition ofmatter of claim 1 wherein M is Si and wherein X is Br.
 11. Thecomposition of matter of claim 1 wherein M is Si and wherein X is Cl.12. A composition of matter comprising: a. a catalyst comprising a metaloxide support structure and an acidic reaction site; b. wherein theacidic reaction site has a composition according to a general formula,

c. wherein X is selected from Br and Cl; d. wherein M is selected fromAl and Si; e. wherein one or more of M and O has a molecular bond withthe metal oxide support structure and f. wherein the catalyst isselected from an aluminum oxide based catalyst and a silicon oxide basedcatalyst.
 13. The composition of matter of claim 12 wherein X is Br. 14.The composition of matter of claim 12 wherein X is Cl.
 15. Thecomposition of matter of claim 12 wherein M is Si.
 16. A composition ofmatter comprising: a. a catalyst comprising a metal oxide supportstructure and an acidic reaction site; b. wherein the acidic reactionsite has a composition according to a general formula,

c. wherein X is selected from Br and Cl; d. wherein M is selected fromAl and Si; e. wherein one or more of M and O has a molecular bond withthe metal oxide support structure and f. wherein the catalyst isselected from an aluminum oxide based catalyst and a silicon oxide basedcatalyst.
 17. The composition of matter of claim 16 wherein X is Br. 18.The composition of matter of claim 16 wherein X is Cl.
 19. Thecomposition of matter of claim 16 wherein M is Al.
 20. The compositionof matter of claim 16 wherein M is Si.
 21. A method of reactinghydrocarbons comprising: a. providing a light hydrocarbon compositionhaving a first constituent molecule and a second constituent molecule;b. providing a catalyst; c. bringing the catalyst in contact with thelight hydrocarbon composition and d. conducting a chemical reaction inwhich the first constituent molecule reacts with the second constituentmolecule to produce a product molecule having a higher molecular weightthan the first constituent molecule; e. wherein the catalyst is selectedfrom an aluminum oxide based catalyst and a silicon oxide based catalystand f. wherein the catalyst is an acidic catalyst.
 22. The method ofclaim 21 wherein the catalyst is a mesoporous catalyst.
 23. The methodof claim 21 wherein the catalyst is a microporous catalyst.
 24. Themethod of claim 21 wherein the catalyst is an aluminum oxide basedcatalyst.
 25. The method of claim 21 wherein the catalyst is a siliconoxide based catalyst.
 26. The method of claim 21 wherein the conductingof the chemical reaction is done in the presence of HBr.
 27. The methodof claim 21 wherein the first constituent molecule is methane and thesecond constituent molecule is methane.